1. Field of the Invention
Poplar trees are part of the genus Populus, comprising many species, some of which can hybridize with other species within the same genus. The poplar tree is a fast growing tree and can grow under a variety of adverse conditions. Their aggressive root system can tap into shallow water tables and, as such, help manage the upward migration of water and soluble salts toward the soil surface. However, several negative physiological effects, e.g., osmotic effects, water stress, and ion imbalance, on poplar trees exposed to salinity may inhibit growth at the cost of carbohydrate production, decreased photosynthesis and stomatal conductance (Neuman, et al. (1996)). There is the need for a type of poplar tree that does not exhibit these negative physiological effects when exposed to salinity.
Irrigation water quality and drainage water disposal have become priority issues for irrigated agriculture in the western San Joaquin Valley of Central California, after inorganic salt contaminants, particularly selenium and boron, were reportedly responsible for waterfowl deformities (Ohlendorf et al., 1986). Evidence suggests that recycling saline water originating from agricultural drainage or from shallow ground waters is desirable over disposing of the saline water (Oster, 1994). Recycling poor quality water for irrigation may have application for more than 250,000 acres of drainage-impacted soils of the Western San Joaquin Valley, but its long-term use requires a critical evaluation that includes irrigation and irrigation delivery systems (Dudley et al., 2008). A practical water reuse strategy in Central California would require the selection of salt and boron tolerant crops and trees for use with waters high in salinity (e.g., 10 dS/m) and boron (10 mg/L) (Lin et al., 2002).
The Integrated on-Farm Drainage Management (IFDM) system expanded the idea of recycling salt-laden drainage water in agricultural systems (Cervinka et al., 1999). Within the IFDM system, trees may offer other advantages over vegetative plants because they transpire larger quantities of water, produce larger biomass, have longer life spans, are deeper rooted, promote greater ecosystem diversity, and re-grow new stems after they have been cut. In previous IFDM implementations, trees, such as Eucalyptus spp. had been planted as border recipient plants for poor quality drainage and surface waters.
2. Description of the Relevant Prior Art
Salt and boron tolerant poplar trees have been selected from screenings occurring on simulated micro-field conditions in Parlier, Calif. (Banuelos, et al. 2010). The micro-field conditions were created by digging 1 m deep pits in Parlier, Calif. and filling the pits with soil (Banuelos, et al. 2010). Poplar trees were planted in the 1 m deep pits and irrigated with waters containing boron and increasing salt levels.
What is needed is the selection of salt and boron tolerant trees to be screened in actual adverse field conditions of the Western San Joaquin Valley.